Two wood workpieces can be fastened together by means of a pocket joint. A pocket joint comprises a pocket hole drilled in a first workpiece at a slant angle to the face of the first workpiece and exiting out of an end face. A second workpiece is then clamped into position in the same plane, abutting the end of the first workpiece adjacent the pocket hole. A screw is then inserted into the pocket hole of the first workpiece and driven into the second workpiece to thereby fasten the second workpiece and first workpiece.
In the prior art, typical jigs provide a drill guide carrier including a first drill guide bushing. In operation, a drill is inserted into the first drill guide bushing and then drilling a first pocket hole. The user then removes the drill from the first drill guide bushing and inserts the drill bit into a second bushing to drill a second parallel pocket hole. The drill is then removed from the second drill guide bushing. The repeating insertion and removal sequences, that may also involve clamping and reclamping the workpiece, are not only time consuming, but also result in dulling and damaging the cutting edge of the drill bit resulting in accelerated drill bit wear due in part to the user's error in slightly misaligning the drill bit with respect to the guide bushings as it is inserted and removed.
There are various methods for clamping the workpiece in a pocket hole drilling jig. Generally, there are two clamping surfaces or jaws that may be tightened by the user to hold the workpiece in the desired position. The actuator for tightening the clamping surfaces may be mechanical or pneumatic. For example, a pneumatic foot switch actuator may be provided for controlling delivery of compressed air to a cylinder that houses a piston to which one of the clamps is attached. This foot operation provides convenience and speed but requires that the user has a supply of compressed air usually requiring a noisy air compressor. Moreover, clamping relatively thick and thin workpieces in the jig with a short stroke pneumatic cylinder requires an additional extension plate for the thinner workpieces, otherwise the jig needs a long base lengthwise to accommodate a long stroke pneumatic cylinder thereon.
Two examples of pocket hole drilling devices with a drill bit that is retained in a drill bit guide carrier are disclosed in U.S. Pat. No. 6,599,064 to Robinson. A drill chuck in such device holds the drill bit; the chuck is rotably coupled to and axially retained in the drill bit guide carrier that is reciprocating and is guided by a retaining structure. The placement of the drill chuck in between the drill bit and the drill bit carrier requires an unnecessary axial space of obstruction that either limits the stroke of the drill bit as will be described or requires a lengthy apparatus in a drilling direction as shown in the Robinson patent.
The maximum size screw used in pocket holes for joining structural lumbers (2×4-38.1 mm×88.9 mm, 2×6-38.1 mm×139.7 mm and so on) is a #8. Joining structural lumbers assemblies that are subject to a high load may require use of larger diameter screws, which demands use of corresponding pocket drill bits and jig.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved device for pocket hole drilling.